OS 10.4 - Network Folders bombing out

One of our users is having problems opening a folder on the network, when she opens the folder it just bombs out and she has to try again, it can sometimes take up to 5 attempts before the folder will open and stay open then she can work away.

I've completely rebuilt the Mac, tried different Network sockets and cables but it still does the same, could this be a problem with the physical NIC in the Mac or is there another explanation?

Any help will be appreciated as i'm stuck now!!